In general, the method of preventing the theft of a vehicle comprises the use of an electrically-operated alarming device or a key-operated locking device. The electrically-operated alarming device is rather effective in providing the theft prevention; nevertheless it is rather vulnerable to a sabotage in view of the fact that it is not protected by a strong and rigid housing. The key-operated locking device is well protected by a strong and rigid housing and is, however, limited in design in that it is not provided with a sound alarm or a luminous alarm.